我如何在接口中重载方法？ [英] How would I overload method in an interface?

问题描述

如果我有这个界面

public interface someInterface {
  // method 1
  public String getValue(String arg1);
  // method 2
  public String getValue(String arg1, String arg2);
}

我希望能够将1或2个字符串传递给getValue方法不必在每个实现类中都覆盖它们。

I want to be able to pass in 1 or 2 string to the getValue method without having to override both in each implementing class.

public class SomeClass1 impelments someInterface 
{
 @Override
 public String getValue(String arg1);
}

public class SomeClass2 implements someInterface 
{
 @Override
 public String getValue(String arg1, String arg2);
}

这不起作用，因为SomeClass1需要实现方法2而SomeClass2需要实施方法1.

this won't work because SomeClass1 needs to implement method 2 and SomeClass2 needs to implement method 1.

我坚持这样做吗？

public interface someInterface2 {
  public String getValue(String... args);
}

public class SomeClass3 implements someInterface2 
{
  @Override
  public String getValue(String... args) {
    if (args.length != 1) {
      throw IllegalArgumentException();
    }
    // code
  }
}

public class SomeClass4 implements someInterface2
{
  @Override
  public String getValue(String... args) {
    if (args.length != 2) {
      throw IllegalArgumentException();
     }
    // code
  }
}

someInterface2 someClass3 = new SomeClass3();
someInterface2 someClass4 = new SomeClass4();
String test1 = someClass3.getValue("String 1");
String test2 = someClass4.getValue("String 1, "String 2");

有没有更好的方法呢？

推荐答案

接口用作用户的合同该接口：指定可用的方法（在所有实现中）以及如何调用它们。如果接口的两个实现需要不同的方法，那么该方法 not 成为界面的一部分：

An interface serves as a contract for the users of that interface: you specify what methods are available (in all implementations) and how they are called. If two implementations of an interface need a different method, then that method should not be part of the interface:

public interface Lookup {
}

public class MapLookup implements Lookup {
    public String getValue(String key) {
        //...
    }
}

public class GuavaLookup implements Lookup {
    public String getValue(String row, String column) {
        // ...
    }
}

在您的程序中，您将知道您使用的是哪种实现，因此您只需调用正确的函数：

In your program, you will know which implementation you use, so you can simply call the right function:

public class Program {
    private Lookup lookup = new MapLookup();

    public void printLookup(String key) {
        // I hardcoded lookup to be of type MapLookup, so I can cast:
        System.out.println(((MapLookup)lookup).getValue(key));
    }
}

替代方法

如果您的类 Program 更通用并使用依赖注入，您可能不知道您拥有哪种实现。然后，我会创建一个新接口 Key ，它可以是键的类型：

If your class Program is more generic and uses dependency injections, you may not know which implementation you have. Then, I would make a new interface Key, which can be either type of key:

public interface Lookup {
    // ...

    public String getValue(Key key);
}

public interface Key {
}

public MapKey implements Key {
    private String key;
    // ...
}

public GuavaKey implements Key {
    private String row, column;
    // ...
}

程序中的依赖注入可能来自一些工厂的实施。由于您无法知道您使用哪种类型的查询，因此您需要一份 getValue 的合约。

The dependency injection in your program might come from some factory implementation. Since you cannot know which type of lookup you use, you need a single contract for getValue.

public interface Factory {
    public Lookup getLookup();
    public Key getKey();
}

public class Program {
    private Lookup lookup;

    public Program(Factory factory) {
        lookup = factory.getLookup();
    }

    public void printLookup(Factory factory) {      
        System.out.println((lookup.getValue(factory.getKey()));
    }
}

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